Understanding the structure and properties of geological formations can reduce the cost of drilling wells for oil and gas exploration. Measurements made in a borehole (i.e., down hole measurements) are typically performed to attain this understanding, to identify the composition and distribution of material that surrounds the measurement device down hole. To obtain such measurements, a variety of sensors and mounting configurations are used.
For example, Logging While Drilling/Measurement While Drilling (LWD/MWD) electromagnetic (EM) logging tools can be used as a mounting platform for downhole sensors. Some projects make use of timing signals provided by clocks located downhole, where an accuracy of about one part in a billion (1 in 109) is useful. However, this order of accuracy is difficult, and in some cases impossible to achieve using conventional techniques.